The boss of defence giant BAE Systems stands to make £18 million almost overnight if the firm's controversial merger with Airbus aircraft manufacturer EADS goes ahead, it has been reported.

Chief executive Ian King has accumulated lucrative share options which would usually take years to mature, but, if the £30billion merger goes through, he would be paid a giant windfall straight away, according to the Daily Mail.

A BAE spokesperson declined to comment.

The newspaper report claims that after 36 years in the company, King has built up extensive holdings of shares and options through a web of executive reward schemes.

He has more than one million BAE shares in his portfolio, worth more than £3.36million at the current price.

In a merger, he would either receive at least that amount in cash or the equivalent value in new shares in the combined group.

King has also amassed options on around 4.5million shares in executive reward schemes set to bear fruit over a number of years.

But a deal with EADS could trigger a "change of control" clause set out in the company's annual report meaning that the shares all pay out at once, according to the report.

This would hand him an instant jackpot of £14.5million, taking his grand total to £17.8million.

It is not clear at this stage whether any or all of these sums will be paid out.

The deal will require the approval of the British, French and German governments if it is to go ahead, while the United States is understood to be taking a close interest in the deal because of BAE's involvement in sensitive US defence projects.

UK unions fear that the move will trigger thousands of job cuts, while the British government is expected to block the deal if it saw the French and German governments take stake above 9 per cent in the new combined entity.

Details of King's potential payday are now likely to be probed by the House of Commons Defence Select Committee, which is holding an inquiry into the proposed merger.

BAE is an expert in defence, security and the military, whereas the majority of EADS' work is commercial.

EADS, a consortium of aerospace and defence manufacturers from France, Germany and Spain, is headquartered in Paris and Berlin. It employs nearly 15,000 people in the UK including at its Airbus wing sites in Filton, near Bristol, and in Broughton, North Wales.